> N[8]:=(9/2)*(1-xi-eta)*eta*(3*eta-1);
> plot3d(N[8],xi=0..1,eta=0..1-xi,axes=boxed,orientation=[-130,60],
> style=wireframe,color=black,thickness=1,scaling=constrained,tickmarks=
> [3,3,3]);

                       9 (1 - xi - eta) eta (3 eta - 1)
               N[8] := --------------------------------
                                      2


> 
